Many hearing devices, such as headsets, hearing aids, and hearing protectors, have tightly sealing earbuds or earcups that occlude ears and isolate the users from environmental noise. This isolation has two side effects when users want to listen to their own-voice (OV), such as when making a phone call or talking to a person nearby without taking the devices off their ears. One of the side effects is the passive loss (PL) at high frequency, which makes the user's own voice sounded muffled to them. The other effect is the amplification of the user's own voice at low frequency, which makes their voice sounded boomy to them. The amplification of a user's own voice at low frequency is commonly referred to as the occlusion effect (OE).
The OE occurs primarily below 1 kHz and is dependent on ear canal structure of the user, the fitting tightness of hearing devices, and the phoneme being pronounced by the user. For example, for front open vowels such as [a:], the OE is usually only several decibels (dB), whereas for back closed vowels such as [i:], the OE can be over 30 dB.
Feedback active noise cancellation (ANC) is a common method used in noise cancelling headphones to compensate for OE. Feedback ANC uses an internal microphone, located near the eardrum, and a headset speaker to form a feedback loop to cancel the sound near the eardrum. Using feedback ANC to counteract OE is described in U.S. Pat. Nos. 4,985,925 and 5,267,321, the content of each of which is hereby incorporated by reference in its entirety. The methods described in these patents require all of the parameters of the feedback ANC to be preset based on an average OE of a user. U.S. Pat. No. 9,020,160, the content of which is hereby incorporated by reference in its entirety, describes updating feedback loop variables of a feedback ANC filter to account for changes in phenomes being pronounced by a user.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.